U.S. Army Research, Development and Engineering Command
Dr. Eric Kathe, US Army RDECOM-ARDEC’s Benet Labs
NDIA, April 2015
Cutting Down the Kick:
Understanding and Managing Large Caliber Recoil
Some Examples of Light Vehicles
General Dynamics
Stryker
Light Armored Vehicle with 105mm
M68 gun
United Defense
M8 Armored Gun System
Light Tank
with 105mm M35 gun
German Wiesel
Airportable Armored Vehicle
with 7 TOW ATGM Missiles
Why?
• Gun Weight • Recoil Force • Vehicle Stability • Thermal Management
• Gun Weight • Recoil Force • Vehicle Stability • Thermal Management
Catch 22
• Airborne Rule:
– Must fit on C130
• Weight limited to < 20ton
• Design of Fighting Vehicle Rule:
– Recoil Should Not Exceed 900 Ns/Metric Ton
• The impulse of a current 120mm tank cannon requires about 32 tons.
• New suspension/ergonomic technology is enabling modest increases in impulse to weight rules of thumb.
Projectile
Charge Gases Recoiling Parts
External
Force Applied
to Gun Conservation of Momentum
Momentum Imparted to Projectile and
Propellant Gases must be Equal and Opposite to
That Imparted to a Freely Recoiling Cannon.
mgun vgun + mcharge vcharge + mprojo vprojo = 0
Basics of Recoil Momentum
Depiction of gun recoil [4].
therefore… vgun = (S Launch Momentum)/ mgun
Recoil Momentum and Energy
• Momentum imparted to the cannon during firing is manifest as kinetic
energy.
KE = 1/2 mgun v2
gun
OBSERVATION: For a given momentum, the kinetic energy of a
recoiling gun is inversely proportional to its mass.
0 500 1000 1500 2000 2500
Recoiling Cannon Mass [Kg]
0
50
100
150
200
250
300
350
400
500
Kin
etic E
ne
rgy o
f R
eco
il [K
J]
Conventional Gun Steel
Carbon Fiber Composite
Potential Weight Reduction with Composites
Composite RAVEN
120mm
120mm With
Brake
Current
120mm
1
2
3
4
5
6
Ge
e L
oa
din
g o
n 1
7to
n V
eh
icle
A
ssu
min
g ½
m (
20
”) R
eco
il S
troke
Composite
120mm With
Brake
450
The Role of a Recoil System
• Recoil systems extract the kinetic energy over the available recoil stroke.
KE = fFrecoil dx Stroke
Flat recoil force profiles result in the lowest maximum
load for a given recoil stroke.
Fo
rce
Recoil Force Versus Stroke
KE y FrecoilGXstroke
Stroke
Methods of Recoil Mitigation
Two Paths:
• Recoil Reduction: Reduce the launch momentum.
– muzzle brakes.
– RArefaction waVE GuN (RAVEN).
• Recoil Management: Deal with recoil more effectively.
– Increase recoil stroke.
– Increase recoil mass.
– Improve vehicle/ground interface.
– Improve man-machine interface.
Momentum Reduction Methods
MMMUUUZZZZZZLLLEEE
BBBRRRAAAKKKEEESSS
Reduced or Reversed Forward Momentum of Charge Gas at/near end of Ballistic Cycle
RRREEECCCOOOIIILLLLLLEEESSSSSS
GGGUUUNNNSSS
Rearward Momentum of Charge Gas or Dummy Projectile During Ballistic Cycle
LLLIIIGGGHHHTTT WWWEEEIIIGGGHHHTTT
PPPRRROOOJJJEEECCCTTTIIILLLEEESSS
Reduced Forward Momentum of Ordnance Projectile &/or Ancillary Structure (e.g. sabots)
Muzzle Brakes
• Typical muzzle brake reduces launch momentum
by 20%
• Blast overpressure and obscuration principle
disadvantages.
Projectile
Charge Gases
Recoilless Guns
• Inefficient ballistics results in
charge masses four times
closed breech gun
requirements.
• High signature and dangerous
back blast.
Projectile
Some of the Charge
Gases Most of the Charge
Gases
RArefaction waVE guN
RAVEN is a hybrid propulsion that achieves: – The thermodynamic efficiency of orthodox guns.
– The recoil advantage of prior recoilless rifles.
– Unprecedented reductions in barrel heating.
– Blast reduction.
“Rarefaction Wave Gun Propulsion,” Kathe, Dillon, Sopok, Witherell, and Dunn,.
http://handle.dtic.mil/100.2/ADA389156
“Sonic Rarefaction Wave Low Recoil Gun,” Kathe and Dillon,
http://handle.dtic.mil/100.2/ADA398942
Late Venting Doesn’t Slow the
Bullet
If the breech of the chamber of a gun is suddenly opened while the projectile is being propelled down the bore, a delay time will occur before the pressure loss at the chamber can be communicated forward to the base of the projectile.
-2 0 2 4 6 8 10
0
50
100
150
200
250
300
350
400
Pre
ssure
[M
Pa
]
Time [ms]
Shot Exit
Venting
Actual Chamber Pressure Data Vented and Non-vented Rounds With Same Muzzle Velocity
58 ksi peak Wave Front
Projo.
Experimental Results
Ejection of
Cartridge Case Head.
Ejection
of Cartridge Case Body,
Bolt Returning to Battery.
Firing
and Venting.
Fir
ing
Vid
eo
Se
qu
en
ce
Fra
me
: 1
9
Fra
me
: 9
Fra
me
: 0
Fra
me
:-
1
630
ms
300
ms
0m
s
-33m
s
Before
Firing.
Ejection
of Cartridge Case Body,
Bolt Returning to Battery.
Bolt-Action Blow-Back Bolt for Proof of Principle
Ph.D.
Rensselaer 2002
NATO Standard 35mm Training Round
Muzzle Velocity
Vented 1,131 m/s
Non-Vented 1,135 m/s
Barrel Heating (ΔT)
Vented 2.13K Non-Vented 3.61K
Measured Momentum
Vented 402 Ns
Non-Vented 1,031 Ns
“Experimental Validation Of Raven Using Standard 35mm Nato TP Ammunition,” Kathe, Glennon, Tortorici, Kertis, and Stamm, JANNAF 38
th Combustion Meeting, Destin, FL, 08 April 2002.
Recoil Management Methods
INCREASED
RECOIL MASS
Recoil energy inversely proportional to recoiling mass
INCREASED
STROKE
Recoil loads inversely proportional to recoil stroke.
FIRE OUT OF
BATTERY
Pre-acceleration of recoiling mass may reduce recoil velocity by as much as 50% with 75% reduction in kinetic energy
ACTIVE
SUSPENSION
Active recoil mitigation suspension may enable vehicle to tolerate greater recoil momentum
Increased Recoil Mass
• Increased recoiling mass is counter productive for
lightweight weapon platforms.
• The potential to leverage “some other” inertia
(such as armor) using a double recoil is intriguing,
yet challenging to implement.
A Double Recoil
Leverages a Second
Sprung Mass.
Increased Stroke
• Increased recoil stroke increases under armor
volume, but is viable for external guns and special
applications.
Turret Integration
• A gun must fit within a turret such that room exists behind the gun sufficient:
– To prevent impact at max recoil extent at all elevations.
– To enable munitions to be loaded.
Fire out of Battery M35
The M35 105mm Tank Gun
A novel recoil method was applied where the cannon was pre-accelerated forward prior to firing. Upon firing, the forward motion of the cannon was reversed, sending it back to a catch latch. This approach may theoretically reduce recoil by a factor of four. By splitting the momentum in half, the max recoil velocity is cut by two, and the kinetic energy is cut by four. Practical consideration reduce performance to a factor of two. Over a 40% reduction was achieved in test.
WEIGHT: …………………..~ 2920 LBS
BARREL LENGTH…………220.5”
RECOIL LENGTH: …………22”
OPERATING PRESSURE: …~90 KSI
“A Fire Out-of-Battery Tank Gun: Theory and Simulation,” Kathe, and Gast,
http://handle.dtic.mil/100.2/ADA402105
Questions
• Thank you for the opportunity to present a tutorial on recoil today.
• Questions are welcome.